The present invention relates to a refrigeration system. Particularly, the present invention relates to an improvement of a refrigeration system which is provided in facilities which require a plurality of types of temperature environment, for example, a supermarket, or the like.
Refrigerated showcases which are provided in a supermarket, or the like, are known in the prior art. A showcase of this type is disclosed in, for example, Japanese Laid-Open Patent Publication No. 62-94785. The showcase includes a refrigerant circuit which is comprised of a compressor, a condenser, an expansion valve and an evaporator which are connected together by a refrigerant pipe. The show case also includes a food display space and an air passageway for producing a cold air.
The evaporator is arranged in the air passageway. A refrigerant which has been discharged from the compressor and condensed in the condenser is depressurized through the expansion valve, and then evaporated by the evaporator while exchanging heat with the air in the air passageway, thereby cooling the air. The cooled air is supplied from the air passageway to the display space to keep the food at a predetermined low temperature. Thus, the freshness of the food is maintained.
The inventors of the present invention have also proposed a refrigeration system which realizes the production of a cold air in a plurality of showcases and general air conditioning in a supermarket store, etc., with a single refrigerating system (Japanese Patent Application No. 9-89164).
The refrigeration system includes a plurality of showcases and an air conditioner for general air conditioning which are connected to a single heat source side unit in parallel to one another. The heat source side unit and each showcase are provided as a secondary refrigerant system. Thus, the above refrigeration system includes a heat source side refrigerant circuit which is comprised of a vapor compression type refrigerating cycle. Each showcase is provided with a user-side refrigerant circuit having a refrigerant heat exchanger for exchanging heat with a refrigerant of the heat source side refrigerant circuit. On the other hand, an evaporator of the heat source side refrigerant circuit is arranged in the general air conditioned room.
Thus, in each showcase, a cold heat of a relatively low temperature (for example, xe2x88x9220xc2x0 C.) is obtained, whereby the freshness of the food can be maintained. On the other hand, in the general air conditioned room, a cold heat of a temperature higher than that in the showcase (for example, 25xc2x0 C.) is obtained, whereby the inside of the store can be cooled.
The present inventors conducted an in-depth study on how to improve the practicability of a refrigeration system as described above which realizes the production of a cold air in a plurality of showcases with a single refrigerating system. The operations required by each individual showcase include those shown below, and the present inventors gave consideration on how to accommodate those operations with a single refrigerating system.
Specifically, the operations required for a showcase include not only the cooling of the air in the showcase but also a defrost operation for melting frost which is performed when the evaporator is frosted. In the prior art, an electric heater is attached to the evaporator, and the defrosting of the showcase is performed by powering the electric heater.
However, in terms of the energy saving property, so-called xe2x80x9chot gas defrostingxe2x80x9d, wherein a refrigerant discharged from the compressor is supplied to the evaporator, is preferred over the defrosting with the electric heater. As described above, each individual showcase may require a cold heat in some cases or may require a hot heat in other cases.
However, where some showcases require a cold heat while the other showcases require a hot heat, these requirements could not be satisfied with prior art circuit configurations.
The present invention has an objective of providing a refrigeration system for performing a so-called xe2x80x9cmulti-stage cascade refrigerating cyclexe2x80x9d as described above, wherein when a plurality of user-side units individually require a hot heat and a cold heat, these requirements can be accommodated with a single refrigerating system.
In order to achieve the above-described object, the first solution includes a plurality of refrigerant heat exchangers for exchanging heat between a heat source side refrigerant and a user-side refrigerant of a multi-stage cascade refrigerating cycle. Each individual refrigerant heat exchanger can be selectively communicated to a high pressure gas pipe, a low pressure gas pipe and a liquid pipe. By selecting the communication state of these pipes, it is possible to individually obtain a heat exchange state for each individual refrigerant heat exchanger.
Specifically, as illustrated in FIG. 1, it includes a heat source side refrigerant circuit (70) having a plurality of refrigerant heat exchangers (50, 60), and a plurality of user-side refrigerant circuits (11, 21) corresponding to the respective refrigerant heat exchangers (50, 60).
The heat source side refrigerant circuit (70) includes compressors (41, 42), first switching means (43, 44), and heat source side heat exchangers (45, 46) which are respectively switched by the first switching means (43, 44) between a state where they are communicated to the discharge side of the compressors (41,42) and another state where they are communicated to the suction side thereof.
One end of a high pressure gas pipe (LG-H) is connected between the discharge side of the compressors (41, 42) and the first switching means (43, 44). One end of a low pressure gas pipe (LG-L) is connected between the suction side of the compressors (41, 42) and the first switching means (43, 44). One end of a liquid pipe (LL) is connected to the liquid side of the heat source side heat exchangers (45, 46).
The pipes (LG-H, LG-L, LL) at the other end are branched into branch pipes (LG-H1, LG-H2, LG-L1, LG-L2, LL1, LL2), respectively.
One end side of the refrigerant heat exchanger (50) of one of the plurality of user-side refrigerant circuits (11, 21) is connected to one of the branch pipes (LL1, LL2) of the liquid pipe (LL). One end side of the refrigerant heat exchanger (60) of the other one of the plurality of user-side refrigerant circuits (11, 21) is connected to the other one of the branch pipes (LL1, LL2) of the liquid pipe (LL).
The other end side of the one refrigerant heat exchanger (50) is configured so as to be switched by second switching means (52) between a state where it is communicated to one of the branch pipes (LG-H1, LG-H2) of the high pressure gas pipe (LG-H) and another state where it is communicated to one of the branch pipes (LG-L1, LG-L2) of the low pressure gas pipe (LG-L).
On the other hand, the other end side of the other one refrigerant heat exchanger (60) is configured so as to be switched by second switching means (62) between a state where it is communicated to the other one of the branch pipes (LG-H1, LG-H2) of the high pressure gas pipe (LG-H) and another state where it i s communicated to the other one of the branch pipes (LG-L1, LG-L2) of the low pressure gas pipe (LG-L).
In addition, the heat source side refrigerant circuit (70) and the user-side refrigerant circuits (11, 21) are configured so that the heat source side refrigerant circulating through the heat source side refrigerant circuit (70) and the user-side refrigerants circulating through the user-side refrigerant circuits (11, 21) exchange heat with each other at the refrigerant heat exchangers (50, 60), thereby performing at multi-stage cascade refrigerating cycle.
By this specific element, the heat exchange state at the respective refrigerant heat exchangers (50, 60) can be desirably changed through a switching operation of the first switching means (43, 44) and the second switching means (52,62). In other words, it is possible to individually set, for each user-side refrigerant circuit (11, 21), a state where a cold heat is supplied thereto and another state where a hot heat is supplied thereto.
For example, some of the refrigerant heat exchangers (50, 60) are communicated to the branch pipes (LG-H1, LG-H2) of the high pressure gas pipe (LG-H) and the other refrigerant heat exchangers (50, 60) to the branch pipes (LG-L1, LG-L2) of the low pressure gas pipe (LG-L) by means of the second switching means (52, 62), while the suction side of the compressors (41, 42) is communicated to the heat source side heat exchangers (45, 46) by means of the first switching means (43, 44). The gas refrigerant which has been discharged from the compressors (41, 42) is supplied to the some of the refrigerant heat exchangers (50, 60) and is condensed while exchanging heat with the user-side refrigerant. Thus, a hot heat is provided to the user-side refrigerant circuits (11, 21).
The condensed refrigerant is supplied to the other refrigerant heat exchangers (50, 60) via the branch pipes (LL1, LL2) of the liquid pipe (LL), and is evaporated while exchanging heat with the user-side refrigerant. Thus, a cold heat is provided to the user-side refrigerant circuits (11, 21). The evaporated refrigerant returns to the suction side of the compressors (41, 42) via the low pressure gas pipe (LG-L) and the heat source side heat exchangers (45, 46).
If the refrigerant heat exchangers (50,60) are communicated to the branch pipes (LG-H1, LG-H2) of the high pressure gas pipe (LG-H) by means of the second switching means (52, 62), while the suction side of the compressors (41, 42) is communicated to the heat source side heat exchangers (45, 46) by means of the first switching means (43, 44), a hot heat is provided to the user-side refrigerant circuits (11, 21) at the respective refrigerant heat exchangers (50, 60). Conversely, if the respective refrigerant heat exchangers (50,60) are communicated to the branch pipes (LG-L1, LG-L2) of the low pressure gas pipe (LG-L) by means of the second switching means (52, 62), while the discharge side of the compressors (41, 42) is communicated to the heat source side heat exchangers (45, 46) by means of the first switching means (43, 44), a cold heat is provided to the user-side refrigerant circuits (11, 21) at the respective refrigerant heat exchangers (50, 60).
In this way, it is possible to individually set, for each user-side refrigerant circuit (11, 21), a state where a cold heat is supplied thereto and another state where a hot heat is supplied thereto.
The second solution is designed so that it is possible to individually adjust a refrigerant circulation operation in the user-side refrigerant circuit performing a multi-stage cascade refrigerating cycle with the heat source side refrigerant circuit, and a heat exchange operation of the heat source side refrigerant circuit at the user-side heat exchanger.
Specifically, as illustrated in FIG. 1, it includes the heat source side refrigerant circuit (70) having the refrigerant heat exchanger (50) and the user-side refrigerant circuit (11).
The heat source side refrigerant circuit (70) includes the compressors (41, 42), the first switching means (43, 44), and the heat source side heat exchangers (45, 46) which are switched by the first switching means (43, 44) between a state where they are communicated to the discharge side of the compressors (41, 42) and another state where they are communicated to the suction side thereof.
One end of the high pressure gas pipe (LG-H) is connected between the discharge side of the compressors (41, 42) and the first switching means (43, 44). One end of the low pressure gas pipe (LG-L) is connected between the suction side of the compressors (41, 42) and the first switching means (43, 44). One end of the liquid pipe (LL) is connected to the liquid side of the heat source side heat exchangers (45, 46).
The pipes (LG-H, LG-L, LL) at the other end are branched into branch pipes (LG-H1, LG-H3, LG-L1, LG-L3, LL1, LL3), respectively.
One end side of the refrigerant heat exchanger (50) is connected to one of the branch pipes (LL1, LL3) of the liquid pipe (LL). The other end side of the refrigerant heat exchanger (50) is configured so as to be switched by the second switching means (52) between a state where it is communicated to one of the branch pipes (LG-H1, LG-H3) of the high pressure gas pipe (LG-H) and another state where it is communicated to one of the branch pipes (LG-L1, LG-L3) of the low pressure gas pipe (LG-L).
Moreover, the heat source side refrigerant circuit (70) and the user-side refrigerant circuit (11) are configured so that the heat source side refrigerant circulating through the heat source side refrigerant circuit (70) and the user-side refrigerant circulating through the user-side refrigerant circuit (11) exchange heat with each other at the refrigerant heat exchanger (50), thereby performing a multi-stage cascade refrigerating cycle.
In addition, it includes another user-side heat exchanger (31) in which one end side thereof is connected to the other one of the branch pipes (LL1, LL3) of the liquid pipe (LL) and the other end side thereof is switched by third switching means (33) between a state where it is communicated to the other one of the branch pipes (LG-H1, LG-H3) of the high pressure gas pipe (LG-H) and another state where it is communicated to the other one of the branch pipes (LG-L1, LG-L3) of the low pressure gas pipe (LG-L).
By this specific element, the heat exchange state at the refrigerant heat exchanger (50) and the user-side heat exchanger (31) can be desirably changed through a switching operation of the first switching means (43, 44), the second switching means (52) and the third switching means (33). In other words, it is possible to individually set a state where a cold heat is supplied to the user-side refrigerant circuit (11) and another state where a hot heat is supplied thereto, and a state where the user-side heat exchanger (31) absorbs heat and another state where it radiates heat.
For example, the refrigerant heat exchanger (50) is communicated to the branch pipe (LG-H1) of the high pressure gas pipe (LG-H) by means of the second switching means (52), and the user-side heat exchanger (31) is communicated to the branch pipe (LG-L1) of the low pressure gas pipe (LG-L) by means of the third switching means (33). The gas refrigerant discharged from the compressors (41, 42) is supplied to the refrigerant heat exchanger (50), and is condensed while exchanging heat with the user-side refrigerant. Thus, a hot heat is provided to the user-side refrigerant circuit (11). The condensed refrigerant is supplied to the user-side heat exchanger (31) via the branch pipe (LL3) of the liquid pipe (LL), and is evaporated. Thus, the heat absorption operation of the user-side heat exchanger (31) is performed. The evaporated refrigerant returns to the suction side of the compressors (41, 42) via the low pressure gas pipe (LG-L).
Conversely, if the refrigerant heat exchanger (50) is communicated to the branch pipe (LG-L1) of the low pressure gas pipe (LG-L) by means of the second switching means (52), and the user-side heat exchanger (31) is communicated to the branch pipe (LG-H3) of the high pressure gas pipe (LG-H) by means of the third switching means (33), the gas refrigerant discharged from the compressors (41, 42) is supplied to the user-side heat exchanger (31) and is condensed. Thus, the heat radiation operation of the user-side heat exchanger (31) is performed. The condensed refrigerant is supplied to the refrigerant heat exchanger (50) via the branch pipe (LL1) of the liquid pipe (LL), and is evaporated while exchanging heat with the user-side refrigerant. Thus, a cold heat is provided to the user-side refrigerant circuit (11). The evaporated refrigerant returns to the suction side of the compressors (41, 42) via the low pressure gas pipe (LG-L).
If the refrigerant heat exchanger (50) is communicated to the branch pipe (LG-H1) of the high pressure gas pipe (LG-H) by means of the second switching means (52), and the user-side heat exchanger (31) is also communicated to the branch pipe (LG-H3) of the high pressure gas pipe (LG-H) by means of the third switching means (33), while the discharge side of the compressors (41, 42) is communicated to the heat source side heat exchangers (45, 46) by means of the first switching means (43, 44), a hot heat is provided to the user-side refrigerant circuit (11) and the heat radiation operation of the user-side heat exchanger (31) is performed.
Conversely, if the refrigerant heat exchanger (50) is communicated to the branch pipe (LG-L1) of the low pressure gas pipe (LG-L) by means of the second switching means (52), and the user-side heat exchanger (31) is also communicated to the branch pipe (LG-L3) of the low pressure gas pipe (LG-L) by means of the third switching means (33), while the suction side of the compressors (41, 42) is communicated to the heat source side heat exchangers (45, 46) by means of the first switching means (43, 44), a cold heat is provided to the user-side refrigerant circuit (11) and the heat absorption operation of the user-side heat exchanger (31) is performed.
In this way, it is possible to individually set, for the user-side refrigerant circuit (11) and the user-side heat exchanger (31), a state where a cold heat is supplied thereto and another state where a hot heat is supplied thereto.
A general air conditioner is required to provide not only cooling but also heating of the inside of the room. In other words, regardless of the operation state of the showcases, a cooling operation is required during the summer time and a heating operation is required during the winder time. Where the showcases require a cold heat while the general air conditioner requires a hot heat, or conversely where the showcases require a hot heat while the general air conditioner requires a cold heat, these requirements could not be satisfied with the prior art circuit configurations. The present solution is capable of satisfying these requirements.
The third and fourth solutions embody the configuration of the second switching means. Specifically, the third solution provides the second switching means (52, 62) as three-way valves (52, 62) which are respectively connected to the branch pipes (LG-H1, LG-H2) of the high pressure gas pipe (LG-H), the branch pipes (LG-L1, LG-L2) of the low pressure gas pipe (LG-L) and the gas side of the refrigerant heat exchangers (50, 60).
The fourth solution provides the third switching means (33) as a three-way valve (33) which is connected to the branch pipe (LG-H3) of the high pressure gas pipe (LG-H), the branch pipe (LG-L3) of the low pressure gas pipe (LG-L) and the gas side of the user-side heat exchanger (31).
The fifth solution embodies an exemplary application of the refrigeration system according to the present invention. Specifically, the user-side refrigerant circuit (11) is provided in a food display showcase (10) provided in a supermarket and is configured so as to perform a vapor compression type refrigerating cycle to cool the space in the showcase with a refrigerant which is evaporated at a showcase heat exchanger (15). On the other hand, the other user-side heat exchanger (31) is a heat exchanger (31) for the air conditioning of the inside of the supermarket.
The sixth solution is designed so that the second switching means (52) communicates the other end side of the refrigerant heat exchanger (50) to the branch pipe (LG-H1) of the high pressure gas pipe (LG-H) when melting the frost on the showcase heat exchanger (15).
By these specific elements, for the showcase (10), it is possible to desirably switch between the cooling of the space in the showcase and the defrosting when it is frosted, and it is also possible to desirably switch the cooling/heating of the general air conditioning.
The seventh solution includes a heat source side unit (40) and a plurality of user-side units (10, 20) which are connected to the heat source side unit (40) by the high pressure gas pipe (LG-H), the low pressure gas pipe (LG-L) and the liquid pipe (LL).
Moreover, it includes the switching means (43, 44, 52, 62) for switching the flow of refrigerant so as to supply the gas refrigerant from the heat source side unit (40) or the gas refrigerant from the user-side unit (10, 20) requiring a cold heat to the user-side unit (10, 20) requiring a hot heat through the high pressure gas pipe (LG-H), and to supply the liquid refrigerant from the heat source side unit (40) or the liquid refrigerant from the user-side unit (10, 20) requiring a hot heat to the user-side unit (10, 20) requiring a cold heat through the liquid pipe (LL).
In addition, the user-side units (10, 20) include circulation circuits (11, 21) through which the user-side refrigerant circulates for exchanging heat with the heat source side refrigerant supplied from the heat source side unit (40) or another one of the user-side units (10, 20), so as to perform a multi-stage cascade refrigerating cycle with the heat source side unit (40).
The eighth solution includes the heat source side unit (40) and a plurality of user-side units (10, 20, 30) which are connected to the heat source side unit (40) via the high pressure gas pipe (LG-H), the low pressure gas pipe (LG-L) and the liquid pipe (LL).
Moreover, it includes the switching means (43, 44, 52, 62, 33) for switching the flow of refrigerant so as to supply the gas refrigerant from the heat source side unit (40) or the gas refrigerant from the user-side unit (10, 20) requiring a cold heat to the user-side unit (10, 20, 30) requiring a hot heat through the high pressure gas pipe (LG-H), and to supply the liquid refrigerant from the heat source side unit (40) or the liquid refrigerant from the user-side unit (10, 20) requiring a hot heat to the user-side unit (10, 20, 30) requiring a cold heat through the liquid pipe (LL).
In addition, at least one user-side unit (10, 20) among the plurality of user-side units (10, 20, 30) includes the circulation circuit (11,21) through which the user-side refrigerant circulates for exchanging heat with the heat source side refrigerant supplied from the heat source side unit (40) or another one of the user-side units (10, 20, 30), so as to perform a multi-stage cascade refrigerating cycle with the heat source side unit (40).
By these specific elements, it is possible to individually set, for each user-side refrigerant circuit (11, 21), a state where a cold heat is supplied thereto and another state where a hot heat is supplied thereto, as in the first and second solutions described above.
As described above, according to the present invention, the following effects are realized.
The first solution provides a refrigeration system including the plurality of refrigerant heat exchangers (50, 60) for exchanging heat between a heat source side refrigerant and a user-side refrigerant of a multi-stage cascade refrigerating cycle which has a configuration such that each individual refrigerant heat exchanger (50, 60) can be selectively communicated to the high pressure gas pipe (LG-H), the low pressure gas pipe (LG-L) and the liquid pipe (LL). By selecting the communication state of these pipes (LG-H, LG-L, LL), it is possible to individually obtain a heat exchange state for each individual refrigerant heat exchanger (50, 60).
The second solution is designed so that it is possible to individually adjust a refrigerant circulation operation in the user-side refrigerant circuit (11) performing a multi-stage cascade refrigerating cycle with the heat source side refrigerant circuit (70), and a heat exchange operation of the heat source side refrigerant circuit (70) at the user-side heat exchanger (31). Thus, it is possible, with a single refrigerating system, to obtain a cold heat and a hot heat according to the requirement from each user-side refrigerant circuit (11, 21) or the user-side heat exchanger (31), whereby it is possible to improve the practicability of a refrigeration system.
If it is designed so that heat can be exchanged between the respective user-side units (10, 20, 30), it is possible to effectively utilize the waste heat. As a result, it is possible to suppress the amount of heat necessary for the heat source side refrigerant which is to be provided to the respective user-side units (10, 20, 30), whereby it is possible to realize an improvement in the energy saving property and a reduction in the running cost associated therewith.
If the switching means (52, 62, 33) for switching the communication state of the pipes (LG-H, LG-L, LL) are provided as three-way valves, it is possible, with a relatively simple configuration and control operation, to obtain a cold heat and a hot heat according to the requirement from each user-side refrigerant circuit (11, 21) or the user-side heat exchanger (31).
Moreover, if the refrigeration system according to the present invention is applied to the food display showcases (10, 20) provided in a supermarket while being used for the air conditioning of the inside of the room, it is possible to individually perform the cooling and defrosting of the showcases (10, 20) and the cooling/heating of the inside of the room. As a result, it is possible, with a single refrigerating system, to ensure the maintenance of the freshness of food and the comfort of the inside of the room.